Welding apparatus



Feb. 20, 1940. STQDDARD r AL Re. 21,369

WELDING APPARATUS Original Filed April 12, 1934 ITNESSES INVENTORS. E047IV. 5f0dda/"d A TOR Y Reissued Feb. 20, 1940 WELDING APPARATUS Ralph N.Stoddard, East Orange, N. J and Edwin H. Vedder, Forest Hills, Pa.,assignors to Westinghouse Electric & Manufacturing Company, EastPittsburgh, Pa., a corporation of Pennsyl- Vania Original No. 2,134,538,dated October 25, 1938,

Serial No. 720,210, April 12, 1934. Application for reissue November 29,1939, Serial No.

16 Claims.

Our invention relates, generally, to electrical control systems and ithas particular relation to control systems for spot welders.

The object of our invention, generally stated,

is to provide a control system for spot welding apparatus which shall besimple, efficient and accurate in operation, and which may be readilyand economically manufactured and installed.

The principal object of our invention is to provide for controlling therelative movement of spot welding electrodes.

Another important object of our invention is to provide for applyingwelding current to the work when a predetermined pressure is appliedthereto and for removing the pressure after welding current ceases toflow.

Another object of our invention is to provide for preventing there-application of pressure to welding electrodes during a predeterminedinterval of time after pressure is removed therefrom.

A further object of our invention is to provide for applying pressure towork to be welded, applying welding current during a predeterminedinterval of time on application of a predetermined welding pressure,relieving the welding pressure on termination of flow of weldingcurrent, and preventing the re-application of welding pressure for apredetermined time interval. Other objects of our invention will, inpart, be obvious and will, in part, appear hereinafter.

Our invention, accordingly, is disclosed in the embodiment hereof shownin the accompanying drawing, and comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of ourinvention, reference may be had to the following detailed description,taken in connection with the accompanying drawing in which the singlefigure illustrates diagrammatically a welding system organized inaccordance with our invention.

When it is desired to make spot welds at a high rate of speed, such as90 to 100 spots per minute, it is desirable to automatically controlboth the movement of the welding electrodes into and out of engagementwith the work, and also to automatically control the time of andduration of application of welding current to the work. In such asystem, it is desirable to provide a single control for the operatorwhich, as long as it is maintained in the operated position, causes thespot welding operations to be auto matically repeated withoutnecessitating any further control on the part of the operator withregard to either moving the welding electrodes or applying the weldingcurrent.

According to our invention, we have provided a pair of weldingelectrodes, one of which is fixed and the other movable as is the usualand customary practice. The movable electrode is urged into engagementwith the work by fluid pressure means which may be initiated intooperation by the closure of the control switch over a normally closedcircuit. When a predetermined pressure is applied to the work, asmeasured by a pressure relay, welding current is applied to perform thewelding operation for a predetermined length of time. At the same time,the normally closed circuit is opened but the circuit is maintainedthrough an auxiliary circuit, so that the opening of the normally closedcircuit at this time has no eifect.

On termination of flow of welding current, the auxiliary circuit isopened, and the fiuid pressure is relieved thereby permitting -themovable electrode to move out of engagement with the work. After theexpiration of a predetermined time interval the normally closed circuitwhich was opened on flow of welding current is again closed, and theforegoing cycle of operations may be successively repeated as long asthe control switch is maintained in the operated condition.

Referring now particularly to the diagram, the reference character Iillustrates, generally, a transformer having a primary winding 2connected by means of a main switch 3, having an operating winding 4, topower conductors 5 and 6 which may be energized by a suitablealtermating-current source 'I, that may be a -cycle generator. Thetransformer l is also provided with a. secondary winding 8, theterminals of which are connected to a fixed electrode 9 and a movableelectrode l0, between which the work to be welded may be positioned.

The movable electrode I0 is connected to a piston H which is slidablypositioned within a cylinder l2. Inlet pipes l3 and I4 are connected tothe cylinder II, as illustrated, in order to apply pressure to the upperand lower sides, respectively, of the piston II.

The piston II is moved both downwardly and upwardly under the influenceof fluid pressure the admission of which is controlled by means of acontrol valve, shown generally at l5, having an operating winding l6 foroperating the valve l5 to one positionto apply pressure to the upperside of the piston I I and another operating winding I! for operatingthe valve l5 to another position to apply pressure to the underside ofthe piston II.. The control valve l5 comprises a rotatable drum isprovided with passageways l9 and which are arranged, in the positionillustrated, to connect the pipe ll to an intake pipe 2| which may beconnected to any suitable source of fluid pressure, such as air, oil orthe like and to connect the pipe It, by means of passageway I9, to anexhaust pipe 22. It will be understood that pressure will then beapplied to the underside of the piston II to maintain the movableelectrode ll out of engagement with the work and that pressure isrelieved from the upper side of the piston ll due to the connection ofthe pipe I! to the exhaust pipe 22.

' An arm 23 is secured to the rotatable drum it, of the valve l5, and ispivotally attached to a rod 24 connecting armatures 25 and 25 which aredisposed to be attracted by the operating windings I6 and I1,respectively. When the operating winding I6 is energized, the armature25 is attracted and the drum I9 is rotated to connect the pipe I! to theintake pipe 2| by means of the passageway l9 while the pipe I4 isconnected, by means of passageway 20 to another exhaust pipe 21.Pressure will thereupon be applied to the upper side of the piston IIand will be relieved from the underside thereof. The movable electrodeID will then be forced into engagement with the work positioned betweenit and the fixed electrode 9.

While the foregoing fluid pressure system has been described asbeing'employed for operating the movable electrode Ill into and out ofengagement with the work to be welded, it will be readily understoodthat any other suitable system may be provided for efl'ecting acorresponding movement of the electrode ill, and that the fluid pressuresystem shown and described herein is used merely for illustrativepurposes.

In order to initiate the cycle of operation of the welding system, acontrol switch, shown generally at 28, is provided. The control switch28 may be of the foot-operated type in order to permit the operator touse his hands for moving the work to be welded between the weldingelectrodes 9 and II) after the completion of each welding operation.

The control switch 28 is disposed to energize the operating winding itof the control valve I5 over a circuit which is normally completed bymeans of contact members 29:: of a timer relay, shown generally at 29,and having an operating winding 30. The function of the timer relay 29is to prevent the re-application of pressure to the work positionedbetween the welding electrodes 9 and III for a predetermined timeinterval after it has been removed therefrom. The timer relay 29 forms apart of an electrode control circuit, shown generally at 3|. Theelectrode control circuit 3| may be energized by means of a transformer,shown generally at 32, having a primary winding 93 connected to theconductors 5 and 5 and a plurality of secondary windings 34, 35, 36 and21. A space discharge device, shown generally at 39, and having an anode39, a grid 40 and a hot cathode I is provided for energizing theoperating winding of the timer relay 29. The space discharge device 38may be of the type which becomes conducting on the application of apredetermined potential to the grid 49 above a characteristic negativeotential.

The space discharge device 95 is :normally maintained in the conductingcondition by means of a positive potential applied thereto from the gridsupply circuit shown generally at 42. As illustrated, the grid supplycircuit 42 is connected for energization across the secondary winding 31of the transformer 82 and a rectifier 43, which may be of thecopper-oxide type, is provided for supplying direct current to thecircuit 42. A capacitor 44 is provided for smoothing out the ripples inthe rectified direct current, while a voltage dividing resistor 55 isprovided for completing the circuit to the grid lll through thesecondary winding 26 of the transformer 32 to provide the desired gridvoltage characteristic. A grid control relay, shown generally at 46,having an operating winding 41, is arranged, when deenergized, toconnect a capacitor 48 through an adjustable potentiometer 49 by meansof contact members 46b to the circuit 42, so that'a positive potentialwill be applied to the grid 40 to normally maintain the space dischargedevice conducting and the winding 39 of timer relay 29 energized.

0n energization of grid control relay 46, contact members 46b areopened, thereby removing the positive potential from the grid andapplying thereto, on closure of contact members 0, a negative potentialfrom the circuit 42, to cause the space discharge device 38 to becomenonconducting, and thereby to effect the deenergization of winding 39 ofthe timer relay 29 The -energization of grid control relay 5 also causescontact members lid to be closed to shunt the contact members 29a oftimer relay 29 and contact members 28a of the foot control switch 29,thereby providing an auxiliary holding circuit for the operating winding[5 of the control valve i5. Contact members a are also opened to preventthe energization of operating winding ll of the control valve I5 on thedeenergization of timer relay 29.

After the operating winding 16 of the control valve l5 has beenenergized, fluid pressure will be applied to the cylinder l2, whichpressure may be measured by means of a pressure relay shown generally at59, that may be adjusted to close contact members 50a on the applicationof a predetermined pressure. The closure of contact members 50acompletes a circuit for energizing a winding 5| of a grid control relay,shown generally at 52, forming a part of a current control circuit,shown generally at 53. The current control circuit 53 may be energizedby means of a transformer, shown generally at 54, having a primarywinding 55 connected to be energized from the conductors 5 and 6, andsecondary windings 55, 51 and 5B.

The energization of grid control relay 52 serves to connect a capacitorto a grid 6| of a space discharge device, shown generally at 62, havingan anode 53 and a hot cathode GI. The space discharge device 62 may besimilar to the space discharge device 38, previously described. Thecapacitor 60 is normally charged with the polarities indicated when thegrid control relay 52 is deenergized because of the asymmetricconducting characteristics of the space discharge device 52.. Thepotential to which the capacitor 60 is charged may be regulated by meansof an adjustable resistor 65, which is connected, for energization, asillustrated, across a portion of the secondary winding 59.

On energization of the grid control relay 52 the capacitor 60 isconnected through resistors 66 and B1 to the grit GI and in seriescircuit relation with an oppositely charged capacitor 88 to the cathode84. The capacitor 88 is normally charged to the potential indicated bymeans of a rectifier 88, which may be 01 the copper-oxide type, thecapacitor 68 and rectifier 88 being connected for energization acrossanother portion of the'secondary winding 58. The capacitor 68, chargedwith the polarities indicated, is provided in order to ensure that thepotential applied to the grid when the capacitor 58 is discharged willbe well below the critical potential of the space discharge device 82,in order to ensure that it will be rendered non-conducting after theexpiration of a predetermined time interval. A resistor 18 is arrangedto be connected across the capacitor 58 when the grid control relay 52is deenergized in order to provide for dissipating the charge applied tothe capacitor 88 when the current control circuit 53 is deenergized.

When the space discharge device 62 is rendered conducting, a circuit iscompleted for energizing winding 14 of an auxiliary switch, showngenerally at 15. The operation of auxiliary switch closes contactmembers 15a which serve to shunt the contact members 50a of. thepressure relay 58. In addition, contact members 15b are closed toconnect one of the discharge resistors 16, 11, 18 or 18, depending uponthe position of the arm 88, in shunt circuit relation with the capacitor88' to effect its discharge. The resistors 15, 11, 18 and 18 areprovided having different resistances so that the time required fordischargingthe capacitor 58 may be varied to correspondingly change thetime during which the space discharge device 82 is maintained in theconducting state. I

The operation of auxiliary switch 15 also closes contact members 150which complete a circuit for energizing the operating winding 4 of themain switch 3 to connect, at contact members 3a and 3b, the primarywinding 2 to the power conductors 5 and 8. Welding current is thereuponapplied to the welding electrodes 8 and I8 and the welding operation isperformed. The closure of contact members 150 also completes a circuitfor energizing the operating winding 81 of the grid control relay 4'6.

After the expiration of the time required to effect the discharge of thecapacitor 50 to reduce the potential applied to the grid 6| of the spacedischarge device 62 below the critical potential, the space dischargedevice 62 is rendered nonconducting, thereby deenergizing operatingwinding 14 of the auxiliary switch 15. Contact members 15c are opened,and operating windings 4 and 41 of the main switch 3 and grid controlrelay .6 are correspondingly deenergized. The main switch 3 is thenopened and the flow of welding current ceases.

The deenergization of grid control relay 48 opens, at contact members"(1, the circuit to the operating winding l6 of the control valve l5 andcompletes, at contact members 45a, a circuit for energizing operatingwinding l1 to operate the control valve l5 back to the position shown inthe drawing. Pressure is thereupon applied to the underside of thepiston II and relieved from the upper side thereof. Although the controlswitch 28 may. still be maintained in the operated position, the circuitto the operating winding It will not be completed due to the fact thatthe operating winding 30 of timer relay 28 is deenergized and contactmembers 28a are opened. After the expiration of a predeterminedinterval,

g which may be adjusted by means of the adjustable resistor 48, thecapacitor 48 will be sufllciently positively charged to apply the properenergizing potential to the grid 48 of the space discharge device 38,which potential will be above the critical potential thereof-and thespace dis charge device 38 will then become conducting. The operatingwinding 38 of the timer relay 28 will again be energized, contactmembers 28a will be closed, and the foregoing cycle of operation may berepeated.

The circuits for effecting the foregoing cycle of operations will now betraced in order to set' forth inmore detail the functioning of our novelcontrol system for spot welders. It will be assumed as set forthhereinbefore that the conductors 5 and 6 are properly energized and thata source of fluid pressure is provided for operating the piston H in thecylinder l2.

On operation of the control switch 28 a circuit is completed fromenergized conductor 5 through conductor 80, contact members 28a, whichare closed when timer relay 28 is energized, conductors 8| and 82,contact members 280. of the control switch 28, conductors 88 and 88,operating winding l8 of the control valve l5 and conductor 85 to theenergized conductor 5.

On the application of a predetermined pressure to the air cylinder l2contact members 50a of tion. The charging circuit may be traced from thegrid 5| through resistor 81, conductor 8l,

contact members 52a, conductor 82, capacitor 60, conductor 83, contactmembers 52d, conductor 84, adjustable resistor 65 and secondary winding58, to the mid-point of the secondary winding 51 which is connected tothe cathode 68.

The energization of grid control relay 52 reverses the connections ofthe capacitor 50 to the grid Si in order to render the space dischargevdevice 62 conducting. This circuit may be traced from the grid 8|through resistor 51, conductor 8|, resistor 66, conductor 85, contactmembers" 520, conductor 83, capacitor 60, conductor 82, contact members52b, conductor 88, capacitor 68 to the secondary winding 58 and to themidpoint of the secondary winding 51.

The application of the energizing potential to v the grid 8! causes thespace discharge device 82 to become. conducting, as set forthhereinbefore, and operating winding 14 of the auxiliary switch 15 isenergized. This circuit may be traced from the secondary winding 58through the space discharge device 62, to the secondary winding 51,conductor 81, operating winding 14 and conductor 80 back to thesecondary winding 55.

The energization of auxiliary switch 15 completes, by the closure ofcontact members 15b, an obvious circuit for discharging the capacitor 88through one of the resistors 16, 11, 18 or 18.

The energization of auxiliary switch 15 also completes a circuit forenergizing the operating winding 4 of the main switch 3 which may betraced from the energized conductor 5 through conductor 88, contactmembers 150, conductor I88, winding 4 of the main switch 3, conductors'llll and 8|, contact members a, and conductor 80 to the energizedconductor 8. Main switch 8 on closing completes, at contact members to,a circuit for shunting contact members 29a of the timer relay 29 sothat, on deenergization of the timer relay 29, the main switch I will bemaintained in the operated position under the control of auxiliaryswitch 18.

The energization oi auxiliary switch 15 also completes a circuit forenergizing grid control relay 46 which may be traced from the energizedconductor 5 through conductor 88, contact members 15c, conductor llll,winding 41 oi relay 49, conductors I02 and BI, contact members 290 andconductor 80 to the energized conductor 6.

The energization of grid control relay 46 completes, at contact members48d, an auxiliary holding circuit for the operating winding l6 0! thecontrol valve l5 which may be traced from energized conductor 6 throughconductor I03, contact members 48d, conductors I04 and B4, winding l6and conductor 85 to the energized conductor 5. As long as the gridcontrol relay 46 remains energized the cycle of operation will not beafiected by the opening of the control switch 28.

The energization of grid control relay 46 opens, at contact members 46b,the charging circuit for capacitor 48 and at contact members 46c,completes a circuit for short circuiting the capacitor 48 and also forapplying a negative potential to the grid over an obvious circuit. Timerrelay 2! which had previously been maintained in the energized positionby the space discharge device 38 over an obvious circuit, is thendeenergized when the space discharge device 38 is no longer maintainedin the conducting state.

The circuit for energizing operating winding ll of the control valve I5is completed on deenergization of grid control relay 46. This circuitmay be traced from theenergized conductor 6, through conductor I05,contact members 460.,

conductor I06, contact members 29b of timer relay 2! which isdeenergized, conductor lll'l, winding ll of the control valve l5, andconductor 85 to the energized conductor 5.

Since certain further changes may be made in the above construction, anddifferent embodiments of the invention may be made without departingfrom the scope thereof, it is intended that all matter contained in theabove description or shown in the accompanying drawing shall beinterpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. Spot welding apparatus comprising, in combination, a pair ofrelatively movable welding electrodes for engaging work means includingmanually operable switching means and pressure fluid supply meanscontrolled by said switching means for moving said electrodes intoengagement with the work under pressure on the operation of saidswitching means, means, operable by the pressure of said fluid, forapplying welding current to said electrodes for a predetermined timeinterval after a predetermined pressure is applied to the work, andmeans for preventing the relaxation of the pressure applied to said workor the reapplicatlon of pressure to said work for a predetermined timeinterval after welding current is applied which is equal in length atleast to said predetermined time interval during which welding currentis applied regardless of the number and character of operations of saidswitching means after the said operation.

2. Spot welding apparatus comprising, in combination, a pair ofrelatively movable welding electrodes for engaging work, manuallyoperable switching means, pressure fluid supply means controlled by saidswitching means, means for moving said electrodes into engagement withthe work under fluid pressure on the operation oi said switching means,means tor applying welding'current to said electrodes for apredetermined time interval, and means for preventing the relaxation oithe pressure applied to said work or the reapplicatlon oil pressure tosaid work for a predetermined time interval after welding current isapplied which is equal in length at least to said predetermined timeinterval during which welding current is applied regardless oi thenumber and character of operations of said switching means after thesaid operation.

3. Spot welding apparatus comprising, in combination, a pair oi.relatively movable welding electrodes for engaging work, pressure fluidsupply means, means actuable by the pressure of said fluid for movingsaid electrodes into engagement with the work under fluid pressure,manually operable means for initiating the functioning of said fluidpressure actuable means, means for applying welding current to the workfor a predetermined time interval, and means for preventing thereapplication of pressure to the work for a predetermined time intervalafter the expiration of said first-mentioned time interval regardless oithe number and character of operations of said manual means after aninitiating operation.

4. Spot welding apparatus comprising, in combination, a pair ofrelatively movable welding electrodes for engaging work, pressure fluidsupply means, means actuable by the pressure of said fluid for movingsaid electrodes into engagement with the work under fluid pressure,manually operable means for initiating the functioning of said actuablemeans, means operable by the pressure of said fluid for applying weldingcurrent to said welding electrodes and work for a predetermined timeinterval after a predeterminedpressure is applied to the work, and meansfor preventing the reapplicatlon of pressure to the work for apredetermined time interval after the expiration of said first-mentionedtime interval regardless of the number and character of operations ofsaid manual means after the initiating operation.

5. Spot welding apparatus comprising, in combination, fixed and movablewelding electrodes disposed to engage opposite sides of work to bewelded, manually operable switching means, pressure fluid supply meanscontrolled by said switching means, means actuable by the pressure ofsaid fluid for causing the movable electrode to engage the work underpressure on the operation of said switching means, means for applyingwelding current to said electrodes and through the work for apredetermined time interval, means for actuating said fluid pres'sureactuable means to relieve the pressure applied to said electrodes afterthe expiration of said time interval, and means for thereafterpreventing the reapplication of pressure to said electrodes for apredetermined time interval regardless of the number and character ofoperations of saidswitching means after the said operation.

6. Spot welding apparatus comprising, in combination,.flxed and movablewelding electrodes disposed to engage opposite sides of work to ,bewelded, manually operable switching means. Dressure fluid supply meanscontrolled by said switching means, means actuable by the pressure ofsaid fluid for causing the movable electrode to engage the work underpressure after said switching means has been operated, means operable bythe pressure of said fluid for applying Welding current to said.electrodes and through the work for a predetermined time interval aftera predetermined pressure is applied to the work, means for actuatingsaid fluid pressure actuable means to relieve the pressure applied tosaid electrodes after the expiration of said time interval, and

means for thereafter preventing the reapplication of pressure to saidelectrodes for a predetermined time interval regardless of the numberand character of the operation of said switching means after the saidoperation.

7. Spot welding apparatus comprising, in combination, a pair ofrelatively movable welding electrodes disposed to oppositely engage Workto be welded, manually operable switching moans. fluid pressure meansoperable to cause the electrodes to engage the work when said switchingmeans is operated, circuit means for applying welding current to saidwelding electrodes and through the work for a predetermined timeinterval, pressure responsive means for initiating the functioning ofsaid circuit means on application of a predetermined pressure to thework, means for relieving the pressure applied by said pressure means tothe work after the expiration of said time interval, and means forthereafter preventing the reapplication of pressure to the work for apredetermined time interval regardless of the number and character ofoperations of said switching means after the said operation.

8. Spot welding apparatus comprising, in combination, fixed and movablewelding electrodes disposed to oppositely engage work to be welded,fluid pressure means operatively connected to the movable electrode forcausing the electrodes to engage the work, manually operable means forinitiating the functioning of said pressure means, a current source,circuit means for connecting the welding electrodes to the currentsource for a predetermined time interval, pressure responsive means forinitiating the functioning of said circuit means on application of apredetermined pressure to the work, means for relieving the pressureapplied by said pressure means to the work after the expiration of saidtime interval, and means for thereafter preventing the reapplication ofpressure to the work 'for a predetermined time interval regardless ofthe number and character of operations of said manual means after theinitiating operation.

9. A system for controlling current flow to and movement of spot weldingelectrodes comprising, in combination, means for applying workingpressure to the electrodes and to work positioned therebetween, anormally closed energizing circuit for said means, means for applyingcurrent to said electrodes and work, means responsive to the operationof said last-named means for opening the normally closed energizingcircuit for said first-named means, and means for maintaining saidcircuit in the open condition for a predetermined time interval toprevent reapplication of pressure to the electrodes during saidinterval.

10. A system for controlling current flow to and movement of spotwelding electrodes comprising, in combination, a normally closedcircuit, means for applying working pressure to the electrodes and workpositioned therebetween, means for energizing said pressure applyingmeans over said normally closed circuit, means for applying weldingcurrent to said electrodes and work for a predetermined time intervalafter a predetermined pressure is applied to the work, means for openingsaid closed circuit at the beginning of said time interval, means forrelieving the pressure applied to the work after the expiration of saidtime interval, and means for preventing the reclosure of said circuitfor a predetermined time interval to prevent reapplication of pressureto the electrodes and work until the expiration thereof.

11. A system for controlling current flow to and movement of spotwelding electrodes comprising, in combination, a normally closedcircuit, means for applying working pressure to the electrodes and workpositioned therebetween, manually operable switch means for energizingsaid pressure applying means over said normally closed circuit, meansfor applying welding current to said electrodes and work for apredetermined time interval after a predetermined pressure is applied tothe work, means operable simultaneously with the application of weldingcurrent for shunting said closed circuit and manual switch means duringthe application of welding current and for opening sa d closed circuit,and means for preventing the reclosure of said circuit forapredetermined time interval after the termination of flow of weldingcurrent to prevent reapplication of pressure to the electrodes and workuntil the expiration thereof.

12. A system for controlling current flow to and movement of spotwelding electrodes comprising, in combination, a timer relay having anoperating winding and contact members disposed to be closed onenergization of said winding, a space discharge device having an anode,a cathode and a grid and connected to a source of alternating current,said operating winding being connected in the anode circuit of saiddevice, circuit means for applying an energizing potential to said gridto render said device conducting, thereby energizing said winding andclosing said contact members, fluid pressure means for operating saidelectrodes into engagement with work to be welded, a control valve forconnecting said pressure means to a fluid pressure supply, a windingconnected in series circuit relation with said contact members foroperating said valve to the intake position, a current source,manuallyoperable switch means disposed to connect said last-namedwinding to said current source, a main switch disposed to connect thewelding electrodes to said current source, means for efiecting theclosure of said main switch for a predetermined time interval, pressuremeasuring means disposed .to initiate the operation of said lastnamedmeans on application of predetermined pressure to the work, and meanseffective simultaneously with the closure of said main switch forshunting said contact members and manual switch means and for renderingsaid space discharge device non-conducting, thereby deenergizing saidtimer relay, said last-named means being eiiective at the expiration ofsaid time interval to deenergize the operating winding of said valve torelieve the pressure applied to the work and to render said spacedischarge device conducting at the expiration of a predetermined timeinterval to energize said timer relay and permit the recurrence of theoperating cycle.

13. In a controller for an electric circuit, in combination, a poweroperated switch for said circuit, manual means to control said switch,and

a power operated device to control said switch, said manual means beingoperable to eiiect operation of said switch to complete said circuit butonly when said power operated device occupies a given position, saidpower operated device being rendered operative each time said circuit iscompleted to move from such'given position to another position to eflectrelease oi said switch and comprising means oi. the time delay type, todelay its aforementioned functioning pending lapse 01' a given time, thesaid time delay means operating to delay said functioning pending lapseof said given time regardless of the number and character of theoperations oi said manual means aiter it has been once operated toeflect operation or said switch, and saidpower operated device iurtherhaving means to render it operable repeatedly to effect repeated cycles01' operation of said switch if said manual means when operated isretained in operated position.

14. Apparatus for timing the periods during which a work-circuit isclosed and open, comprising: on-timing means for controlling theduration of the closed period; and ofl-timing means for controlling theduration 01 the open period between successive closed periods; one ofsaid timing means including means responsive to a predeterminedelectro-motive-force for causing termination of its respective periodand for eilecting initial operation of the other of said timing means,and manually operable means for initiating the operation 01' said onetiming means, said timing means operating for their characteristic timeperiods after an initiating operation regardless of the number andcharacter of operations of said manually operable means alter the saidinitiating operation. 4

15. Apparatus for timing the periods during which a work-circuit isclosed and open, comprising: on-timing means for controlling theduration of the closed period; and ofl-timing means for controlling theduration of the open period between successive closed periods; one ofsaid timing means including means responsive to a predeterminedelectro-motive-iorc'e for causing termination of its respective periodand, for eiiecting initial operation of the other of said timing means,and also including means for altering the value of theelectro-motive-force applied to said one timing means to saidpredetermined electro-motive-force required to effect operation of saidresponsive means, manually operable means for initiating the operationof said one timing means, and means for assuring that said timing meansfunction for their characteristic periods independently of the numberand character 01' operations of said manually operable means after aninitiating operation.

16. Apparatus for timing the periods during which a work-circuit isclosed and open, comprising: on-timing means for controlling theduration 01 the closed period; and off-timing means for controlling theduration of the open period between successive closed periods; theduration of one 01' said periods being dependent upon the magnitude oithe voltage applied to one of said timing means, said one period beinggreater for small voltages applied to said one timing means and less forlarge voltages; said one/timing means including means for causingtermination of said one period and for eflecting initial operation ofthe other of said timing means, manually operable means for effectinginitiation of said one timing means, and means for assuring that saidtiming means function for their characteristic periods independently ofthe number and character of operations of said manually operable meansafter an initiating operation.

. RALPH N. STODDARD.

EDWIN I-I. VEDDER.

